-LRB- CNN -RRB- -- Ousted Libyan leader Moammar Gadhafi 's hometown of Sirte will fall soon , perhaps within days , commanders of the anti-Gadhafi operation told U.S. Defense Secretary Leon Panetta on Friday , according to a senior U.S. defense official traveling with him .

Panetta met during the morning with the commanders at the naval base that hosts the U.S. Sixth Fleet in Italy , the official said .

The commanders said they have no reason to believe Gadhafi can exercise command and control of those militia members who remain loyal to him , the official said .

They further believe that , although the anti-Gadhafi forces are gaining the ability to exercise control , they will likely need training to develop their capabilities , the official said .

Still , no timetable has been drawn up for when commanders will recommend that NATO forces end their involvement , the official said .

The fall of Sirte could not come soon enough for Libya 's new leaders , eager to declare liberation once the birthplace of Gadhafi is under their control .

But battles for the coastal city southeast of Tripoli have raged for weeks as Gadhafi loyalists dug in to put up stiff resistance .

Complicating the matter was the resignation Friday of Mahdi al-Harati , the deputy head of the Tripoli Military Council , a senior National Transitional Council official said . `` He resigned due to differences with the NTC on the planning of the security of Tripoli . We are the official governing body and the efforts of the revolutionaries that fought for the liberation are appreciated but the command must be centralized , '' Mohamed Sayeh told CNN .

He said NTC officials were trying to get that message across `` in a democratic , brotherly manner . ''

Al-Harati will continue as commander of the Tripoli brigades , said Fathi al-Wersali , a senior member of the Tripoli Military Council . `` There is overlapping in the role of the Tripoli military council and the NTC , '' he said . `` A clear mechanism has not been finalized , which leaves us not clear on how to move forward in securing Tripoli . ''

Early Friday , hundreds of revolutionary fighters attacked from the west , NTC military field commanders said .

Gadhafi 's men control tall buildings in the city center , where they fire on their foes from rooftops . They were striking with rocket-propelled grenades and machine guns , said the council 's commanders , Mohammed Ibrahim and Jamal al-Raeis , from the front lines .

At least 12 revolutionary fighters were killed and 193 others wounded Friday , the Misrata Military Council said .

`` The battle will be difficult , but we have to finish it , '' Ibrahim said .

The International Committee of the Red Cross evacuated three wounded people from Ibn Sina hospital in Sirte to a field hospital on Thursday .

Dibeh Fakhr , an ICRC spokesman in Misrata , said Friday that the group is committed to re-entering Sirte to evacuate more casualties .

The Red Cross said thousands of civilians remain inside Sirte and waves of war-weary civilians were streaming from the coastal city every day .

`` We even saw entire families leaving on foot , bringing their small children with them , without any food or water , '' Red Cross delegate Ghafar Bishtawi said .

More than 18,000 people , including many women , children and elderly people , are displaced east of Sirte and hundreds have moved to safer locations west of the city , the Red Cross said .

Sirte is one of two contested cities remaining in Libya as the National Transitional Council moves forward to form new governance in the country .

The council 's leader and the interim prime minister have promised to step down to clear the way for a new government once Sirte is taken .

Gadhafi , wanted by the International Criminal Court in the Hague for alleged crimes against humanity , has not been seen in public in months . Syrian-based television aired an audio message Thursday that was purportedly from the deposed leader . In it , the speaker urged Libyans to protest the new leadership .

CNN 's Mohammed Tawfeeq and journalist Mohamed Fadel Fahmy contributed to this report .

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Deputy head of Tripoli Military Council resigns

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Anti-Gadhafi commanders : No reason to believe Gadhafi can exercise command

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Revolutionary fighters launched a western Sirte offensive

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Gadhafi 's men have put up resistance in Sirte and Bani Walid for weeks